Photographing apparatus, photographing method and a computer readable medium of instructions for controlling the photographing apparatus

ABSTRACT

A photographing apparatus and method that can prevent a resolution of a peripheral portion of an image from being degraded with a simple structure. The photographing apparatus and method employ an in-focus state detector for detecting evaluation values for auto in-focus operation representing an in-focus state of a photographing image from a first in-focus state detection region disposed on a center portion of the photographing image, and at least one second in-focus state detection region disposed on a peripheral portion of the photographing image, a flat subject determiner that determines whether a subject is a flat subject based on the detection result of the evaluation values for auto in-focus operation, a flat subject focusing position calculator that calculates a final focusing position based on the evaluation values when the subject is determined as being a flat subject, and a three-dimensional subject focusing position calculator that calculates a final focusing position based on the evaluation value when it is determined that the subject is not a flat subject.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application claims the benefit of Japanese Patent Application No.2006-356035, filed on Dec. 28, 2006, in the Japanese IntellectualProperty Office, the disclosure of which is incorporated herein in itsentirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a photographing apparatus and aphotographing method, and more particularly, to a photographingapparatus and a photographing method that can prevent a resolution atperipheral portions of an image from being degraded.

2. Description of the Related Art

In auto-focusing (AF) cameras which can perform auto-focus adjustment,when the focusing is performed based on a center of a photographingregion, defocusing of peripheral portions of the photographing regioncan become worse due to aberrations in a photographing lens. Therefore,in Japanese Laid-open Patent No. 2006-189580, an average field curvatureratio, that is an average value of field curvature ratios with respectto an entire region of a photographing surface, is calculated, and thephotographing lens is moved according to the average field curvatureratio.

However, in a case where a principal subject does not exist on theperipheral portion of the image, for example, when a generalthree-dimensional subject is photographed, there is no need to focus onthe peripheral portion. In this case, defocusing of the peripheralportion can be required in order to emphasize the perspective of thesubject. When the method of calculating the average field curvatureratio disclosed in the Japanese Laid-open Patent Publication No.2006-189580 is applied, the processing needed to perform thephotographing is excessively increased, and it thus requires much timeto photograph the subject.

Also, in a case where a sheet of paper on which letters are printed isphotographed, the center of the photographing region and the peripheralportion of the photographing region must be clearly focused, and thus,it is desirable to restrict degradation of resolution at the peripheralportions.

SUMMARY OF THE INVENTION

The present invention provides a photographing apparatus having a simplestructure that can prevent a resolution at peripheral portions of animage from being degraded, and a photographing method.

An embodiment of the present invention thus provides a photographingapparatus including an in-focus state detector for detecting evaluationvalues for auto in-focus operation representing an in-focus state of aphotographing image from a first in-focus state detection regiondisposed on a center portion of the photographing image, and at leastone second in-focus state detection region disposed on a peripheralportion of the photographing image; a flat subject determiner thatdetermines whether a subject to be photographed is a flat subject (e.g.,a substantially flat subject) or not based on the detection result ofthe evaluation values for auto in-focus operation; and a flat subjectfocusing position calculator that calculates a final focusing positionbased on the evaluation values for auto in-focus operation obtained fromthe first and second in-focus detection regions, when the subject isdetermined as a flat subject by the flat subject determiner. Theapparatus further includes a three-dimensional subject focusing positioncalculator that calculates a final focusing position based on theevaluation value for auto in-focus operation obtained from the firstdetection region, when it is determined that the subject is not a flatsubject by the flat subject determiner.

According to the above apparatus, an evaluation value for auto in-focusoperation is detected from a first in-focus detection region disposed ona center portion of the photographed image and one or more secondin-focus detection region disposed on a peripheral portion of thephotographed image. In addition, it is determined whether the subject isa flat subject or not based on a detection result of the evaluationvalue for auto in-focus operation. In a case where the subject isdetermined to be the flat subject, a final focusing position iscalculated based on the evaluation values for auto in-focus operationfrom the first and second in-focus detection regions. In addition, in acase where the subject is determined not to be the flat subject, thefinal focusing position is calculated based on only the evaluationvalues for auto in-focus operation from the first in-focus detectionregion. Therefore, the final focusing position is determined so thatpeak of the evaluation values for the auto in-focus operation of thecenter in-focus detection regions and the in-focus state focusingpositions of the peripheral in-focus detection regions can exist in arange of the predetermined allowable defocused amount, and thus, theresolution of the peripheral portion can be improved without excessivelydegrading the resolution of the center portion.

The flat subject determiner may also determine whether the subject is aflat subject based on a difference between a focusing position where theevaluation value for auto in-focus operation of the first in-focusdetection region is a maximum and a focusing position where theevaluation value for auto in-focus operation of the second in-focusdetection region is a maximum. In addition, when the difference betweenthe focusing position where the evaluation value for auto in-focusoperation of the first in-focus detection region and the focusingposition where the evaluation value for auto in-focus operation of thesecond in-focus detection region is within the range of the allowabledefocused amount, it can be determined that the subject is the flatsubject.

The photographing apparatus may further include a display unitdisplaying the photographing image, such that the first in-focusdetection region may be displayed on the display unit with thephotographing image, and the second in-focus detection region is notdisplayed on the display unit. According to this arrangement, since thesecond in-focus detection region is not displayed on the display unit,the resolution of the peripheral portion of the flat subject can beimproved while the user does not recognize the second in-focus detectionregion.

The photographing apparatus may further include a diaphragm valuecontroller that changes the diaphragm value based on the determinationresult of the flat subject determiner. According to this arrangement,the allowable defocused amount can be expanded by reducing the diaphragmvalue, and thus, the resolution of the peripheral portion of the imagecan be improved.

The photographing apparatus may further include a contour emphasizingcontroller that changes a process of emphasizing a contour of the imagebased on the determination result of the flat subject determiner.Therefore, the resolution of the peripheral portion of the image can beimproved by performing the contour emphasizing operation.

The photographing apparatus may further include a posture determinerthat determines a posture of the photographing apparatus based on theevaluation values for auto in-focus operation of the first and secondin-focus detection regions. According to this arrangement, a posture ofthe photographing apparatus can be determined, and thus, the exposurecan be optimally adjusted according to the posture of the photographingapparatus.

Another embodiment of the present invention provides a photographingmethod comprising the operations of detecting evaluation values for autoin-focus operation, which represent in-focus states, from a firstin-focus detection region on a center portion of a photographing imageand at least one second in-focus detection region on a peripheralportion of the photographing image; determining whether a subject to bephotographed is a flat subject based on the result of detecting theevaluation values for auto in-focus operation from the first and secondin-focus detection regions; calculating a final focusing position basedon the evaluation values for auto in-focus operation from the first andsecond in-focus detection regions if the subject is determined as a flatsubject; and calculating a final focusing position based on theevaluation value for the auto in-focus operation obtained from the firstin-focus detection region if the subject is determined to not be a flatsubject.

In determining whether the subject is a flat subject, the flat subjectmay be determined based on a difference between a focusing positionwhere the evaluation value for auto in-focus operation of the firstin-focus detection region is a maximum and a focusing position where theevaluation value for auto in-focus operation of the second in-focusdetection region is a maximum.

The photographing method may further include the operation of displayingthe photographing image, wherein the first in-focus detection region isdisplayed with the photographing image, and the second in-focusdetection region is not displayed.

In determining whether the subject is a flat subject, diaphragm valuemay be changed based on the result of determining whether the subject isa flat subject. In determining whether the subject is a flat subject, aprocess of emphasizing a contour of the image may be changed based onthe result of determining whether the subject is a flat subject.

The photographing method may further include the operation ofdetermining a posture of the photographing apparatus based on theevaluation values for auto in-focus operation of the first and secondin-focus detection regions.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent by describing in detail exemplary embodimentsthereof with reference to the attached drawings in which:

FIG. 1 is a diagram illustrating an example of a structure of aphotographing apparatus according to an embodiment of the presentinvention;

FIG. 2 is a figure showing an example of a detection region of anin-focus position (in-focus detection region) formed in a region of animage to be photographed;

FIG. 3 is a graph illustrating exemplary evaluation values for autoin-focus operation obtained in the in-focus detection regions when thesubject of FIG. 2 is photographed;

FIG. 4 is a table showing exemplary the evaluation values for the autoin-focus operation of FIG. 3 and data including focusing positions(distances to subject);

FIG. 5 is a figure showing an example of a flat subject, that is, asheet of paper on which characters are printed, disposed inperpendicular to an optical axis and photographed;

FIG. 6 is a graph showing exemplary evaluation values for auto in-focusoperation obtained in the in-focus detection regions in a case where theflat subject of FIG. 5 is photographed;

FIG. 7 is a table showing exemplary evaluation values for the autoin-focus operation of FIG. 6 and data of focusing positions (distancesto the subject) corresponding to each other;

FIG. 8 is a graph showing, in detail, a portion around the focusingposition of FIG. 6;

FIG. 9 is a figure showing the subject of FIG. 2 that is photographed ina longitudinal direction;

FIG. 10 is a graph showing exemplary evaluation values for auto in-focusoperation obtained in in-focus detection regions in a case where thephotographing is performed in the state of FIG. 9; and

FIG. 11 is a flowchart illustrating exemplary operations of thephotographing apparatus according to the embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to accompanying drawings. In the drawings, like referencenumerals denote like elements.

FIG. 1 is a diagram showing an example of a structure of a photographingapparatus according to an embodiment of the present invention. Referringto FIG. 1, the photographing apparatus 100 according to this exemplaryembodiment includes a zoom lens (group) 102, a combined diaphragm andshutter 104, a focus lens (group) 108, a charge coupled device (CCD) 110as an imaging device, an amplifier integrated correlated double sampling(CDS) circuit 112, an analog/digital (A/D) converter 114, and an imageinput controller 116. The photographing apparatus 100 further comprisesan image signal processor 118, a compression processor 122, a liquidcrystal display (LCD) driver 124, an LCD 126, a timing generator 128, acentral processing unit (CPU) 150, a controller 130, a shutter button132, a memory 134, a video random access memory (VRAM) 136, a mediacontroller 138, a recording medium 140, and drivers 142, 144, and 146.

The zoom lens 102, the combined diaphragm and shutter 104, and the focuslens 108 are driven by actuators that are controlled by the drivers 142,144, and 146, respectively. The zoom lens 102 in this example is movedback and forth along an optical axis direction, and changes a focaldistance continuously. The combined diaphragm and shutter 104 controlsan exposure time of the CCD 110 when an image is photographed, and atthe same time, controls an amount of light incident into the CCD 110.The focus lens 108 is moved back and forth along the optical axisdirection, and controls the focus of the image formed on the CCD 110.The CCD 110 is a device for converting the light incident through thezoom lens 102, the combined diaphragm and shutter 104, and the focuslens 108 into electric signals.

In addition, in this embodiment, the CCD 110 is used as an imagingdevice, and the present invention is not limited thereto, that is, acomplementary metal oxide semiconductor (CMOS) device or other imagingsensors can be used as the photographing device instead of using the CCD110. The CMOS device can convert the light from a photographing subjectinto an electric signal faster than the CCD does, and thus, a time takenfor processing a combination of images after photographing the imagescan be reduced.

The CDS circuit 112 is a circuit in which a CDS circuit that is a kindof sampling circuit for removing noise of the electric signal outputfrom the CCD 110 and an amplifier that amplifies the electric signalafter removing the noise are integrated. In this embodiment, thecircuit, in which the CDS circuit and the amplifier are integrated, isused, however, the CDS circuit and the amplifier can be separated tooperate independently.

The A/D converter 114 converts the electric signal generated in the CCD110 into a digital signal, and generates raw data of the image (imagedata). The image input controller 116 controls an input of the raw dataof the image (image data) generated by the A/D converter 114 into thememory 134.

The image signal processor 118 calculates an evaluation value forauto-focusing (AF evaluation value) as contrast information from theimage data output from the CCD. In addition, the image signal processor118 compensates a gain of the light amount, processes an edge of theimage (contour emphasizing process), and controls a white balance withrespect to the image data output from the CCD 110.

The compression processor 122 compresses the image data output from theCCD 110 as image data of an appropriate format. The compression formatcan be a reversible format or a nonreciprocal format. As an example ofthe compression format, the image data can be converted into JoinPhotographing Experts Group (JPEG) format or JPEG 2000 format.

The LCD 126 displays a live view before performing the photographingoperation, setting screen of the photographing apparatus 200, or thephotographed image. The image data or the information of thephotographing apparatus 100 can be displayed on the LCD 126 using theLCD driver 124.

The timing generator 128 inputs a timing signal into the CCD 110. Thatis, the operation of the CCD 110 is controlled by the timing signal ofthe timing generator 128. The timing generator 128 can make the CCD 110operate for a specific period of time only, and thus, allow the CCD 110to have a function of electronic shutter.

The CPU 150 performs a signal-based command with respect to the CCD 110or the CDS circuit 112, or performs an operation-based command accordingto the operations of the controller 130 and the shutter button 132. Inthis embodiment, one CPU is formed, however, the signal-based commandand the operation-based command can be performed in separate CPUs.

The controller 130 includes a member for performing the operation of thephotographing apparatus 100 or performing various settings when thephotographing is performed. The member disposed in the controller 130includes a power button, a cross button for selecting a photographingmode or a photographing drive mode and setting effect parameters, and aselection button.

The shutter button 132 is a button for performing the photographingoperation. When the shutter button 132 is in a half-pushed state(hereinafter, the half-pushed state of the shutter button 132 isreferred to as SH1), an AF operation for driving the focus lens 108 ontoa focusing position, and when the shutter button 132 is full-pushed(hereinafter, the full-pushed state of the shutter button 132 isreferred to as SH2 state), an exposure of the CCD 110 is performed andthe subject is photographed.

The memory 134 temporarily stores the photographed images. The memory134 has a storage capacity that can store a plurality of images. Thereading/writing of the images from/onto the memory 134 are controlled bythe image input controller 116.

The VRAM 136 maintains the contents displayed on the LCD 126, and aresolution or the maximum number of color emission of the LCD 126 isdependent on the capacity of the VRAM 136. The recording medium 140records the photographed image. Input/output of the images into/from therecording medium 140 are controlled by the media controller 138. Amemory card that is a card type memory device, in which the data isrecorded in a flash memory, can be used as the recording medium 140.

The CPU 150 includes an appropriate auto exposure (AE) level calculator152, an exposure controller 154, an in-focus position detector 156, aflat subject determiner 158, and a camera posture determiner 160. Theappropriate AE level calculator 152 performs an auto exposure of thephotographing apparatus 100, and obtains an exposure value (EV). Theappropriate AE level calculator 152 calculates an AE evaluation value ofthe photographing and the AE evaluation value can be calculated by theimage signal processor 118.

The exposure controller 154 determines a diaphragm value and a shutterspeed when the subject is photographed based on the AE evaluation valuecalculated by the appropriate AE level calculator 154. The driver 144 iscontrolled by the determined diaphragm value and the shutter speed.

The in-focus position detector 156 detects a focusing position of thesubject from the evaluation value for auto in-focus operation of theimage data generated in the image signal processor 118 when the imagelight is incident into the CCD 110 from the subject.

The flat subject determiner 158 determines whether the subject is a flatsubject or not from the in-focus position of the subject detected by thein-focus position detector 156. As can be appreciated by one skilled inthe art, the term “flat subject” can also refer to and be interpreted asa “substantially flat subject.” In addition, the camera posturedeterminer 160 determines the posture of the photographing apparatus 100at the in-focus position of the subject detected by the in-focusposition detector 156. In addition, the CPU 150 calculates a finalfocusing position in each of the cases where the subject is determinedas the flat subject and determined as a three-dimensional subject, andthen, transmits a command for driving the focus lens 108 onto the finalfocusing position to the driver 146.

FIG. 2 is a figure showing an example of detection regions of thein-focus positions (in-focus detection regions 200 through 208) formedin the photographing image region. As shown in FIG. 2, three in-focusdetection regions 200 a, 200 b, and 200 c are formed on a center portionof the photographing image region, and four in-focus detection regions202, 204, 206, and 208 are formed on a peripheral portion of thephotographing image region.

The in-focus detection regions 200 a, 200 b, and 200 c are arranged in arow in a horizontal direction on the center portion of the photographingimage region. In addition, the in-focus detection regions 202, 204, 206,and 208 are formed at the four corners of the photographing imageregions. The three in-focus detections regions 200 a, 200 b, and 200 con the center portion are displayed on the LCD 126 or a finder (notshown) of the photographing apparatus 100. The four in-focus detectionregions 202, 204, 206, and 208 on the peripheral portion are notdisplayed on the LCD 126 or on the finder. Therefore, a user of thephotographing apparatus 100 can recognize the positions of the in-focusdetection regions 200 a, 200 b, and 200 c on the screen, however, theuser cannot recognize the in-focus detection regions 202, 204, 206, and208.

The evaluation value for auto in-focus operation is calculated from theimage data output from the CCD 110 onto each of the in-focus detectionregions 200 a, 200 b, 200 c, 202, 204, 206, and 208. FIG. 3 is a graphshowing exemplary evaluation values for the auto in-focus operationobtained from the in-focus detection regions 200 a, 200 b, 200 c, 202,204, 206, and 208 when the subject of FIG. 2 is photographed. In FIG. 3,a vertical axis represents the evaluation value for the auto in-focusoperation, and a horizontal axis represents focusing positions(distances to the subject). In addition, FIG. 4 is a table showingexemplary evaluation values for the auto in-focus operation and thefocusing positions (distances to the subject) corresponding to eachother.

As shown in FIGS. 3 and 4, when the focus lens 108 is driven, theevaluation values for the auto in-focus operation with respect to eachof the steps of the focusing positions from infinity to a minimum focallength (0.5 m) are obtained. The focusing position represents theposition of the focus lens 108. The farthest position of the focus lens108 is set as 0, the step increases when the focus lens moves, and whenthe position of the focus lens is on the nearest position (0.5 m), thestep becomes the maximum value (which is equal to focusing position 30as shown in FIG. 4).

In each of the in-focus detection regions 200 a, 200 b, 200 c, 202, 204,206, and 208, the image is clearly focused, that is, in an in-focusstate, at the position of the focus lens 108 where the evaluation valuefor the auto in-focus operation is the largest. Here, the focusingposition in the in-focus state is referred to as an in-focus statefocusing position.

FIGS. 3 and 4 represent an example of the characteristics when a generalthree-dimensional subject shown in FIG. 2 is photographed, for example,when an animal (a dog) is photographed on the outdoor location. In acase of the three-dimensional subject, the in-focus state focusingpositions in each of the in-focus detection regions 200 a, 200 b, 200 c,202, 204, 206, and 208 are different from each other. For example, thein-focus detection regions 200 a, 200 b, and 200 c on the center portioncorrespond to the position of the dog, that is, the subject, and thus,the distance to the subject is about 0.79 m to 0.83 m (in-focus statefocusing positions: 18-19). In addition, the in-focus detection regions202 and 204 on upper corners correspond to the position of a wall, andthus, the distance to the subject is about 1.15 m to 1.25 m (in-focusstate focusing positions: 12-13). In addition, the in-focus detectionregions 206 and 208 on lower two corners correspond to the position of aground that is in front of the dog, and thus, the distance to thesubject is about 0.65 m (in-focus state focusing position: 23).

FIG. 5 shows an example of a state where a sheet of paper on whichcharacters are printed is arranged perpendicular to an optical axis ofthe zoom lens 102 and the focus lens 108 and is photographed. FIG. 6shows exemplary evaluation values for the auto in-focus operationobtained from the in-focus detection regions 200 a, 200 b, 200 c, 202,204, 206, and 208 in a case where the flat subject of FIG. 5 isphotographed. In addition, FIG. 7 is a table showing exemplaryevaluation values for the auto in-focus operation and the focusingpositions (distances to the subject) corresponding to each other.

In a case of the flat subject, the distances to the subject at thein-focus detection regions 200 a, 200 b, 200 c, 202, 204, 206, and 208are the same as each other, and thus, the in-focus state focusingpositions of the in-focus detection regions 200 a, 200 b, 200 c, 202,204, 206, and 208 are identical to each other. However, as shown inFIGS. 5 and 6, the in-focus state focusing positions on the peripheralportion are nearer than the in-focus state focusing positions on thecenter portion are because of an aberration of the lens.

Therefore, the in-focus state focusing position obtained from the threein-focus detection regions 200 a, 200 b, and 200 c on the center portionis at step 19, and when the focus lens 108 is driven to the position,the best focusing position is obtained at the center portion. However,the in-focus state focusing position of the peripheral portion is atstep 23, and thus, the focus at the peripheral portion is different fromthe best focus position of the center portion by about 4 steps. Inaddition, if the in-focus state focusing position of the peripheralportion is different from the in-focus state focusing position of thecenter portion by more than an allowable defocus amount, the degradationof the resolution at the peripheral portion cannot satisfy a standard ofthe image quality.

The allowable defocus amount will be described as follows. When it isassumed that a pitch of the pixel in the imaging device is 2 μm, thefocusing distance (f) of the lens is 6.3 mm, and FNo. of the diaphragmis F2.8, a diameter of an allowable circuit of confusion can becalculated by following Equation 1.

Diameter of circle of confusion=2[μm]×√{square root over (2)}=2√{squareroot over (2)}[μm]  (1)

In addition, since the allowable defocus amount can be calculated bymultiplying the diameter of the allowable circle of confusion with thediaphragm value, and thus, can be represented as following Equation 2.

$\begin{matrix}\begin{matrix}{{{{allowable}\mspace{14mu} {defocus}\mspace{14mu} {amount}} = {{diameter}\mspace{14mu} {of}\mspace{14mu} {allowable}}}\mspace{31mu}} \\{{{circle}\mspace{14mu} {of}\mspace{14mu} {confusion} \times {{FNo}.}}} \\{= {2\sqrt{2} \times 2.8}} \\{\approx {8\mspace{11mu}\lbrack{µm}\rbrack}}\end{matrix} & (2)\end{matrix}$

In addition, a defocused amount (DF) to the subject can be calculatedusing following Equation 3.

$\begin{matrix}{{DF} = {{f \times \frac{f}{{distance}\mspace{14mu} {to}\mspace{14mu} {subject}}} - {f \times \frac{f}{{distance}\mspace{14mu} {to}\mspace{14mu} {subject}\mspace{14mu} {currently}\mspace{14mu} {focused}}}}} & (3)\end{matrix}$

From the above Equation 3, in the photographing apparatus 100 of thecurrent embodiment, the allowable defocused amount is about 3 steps ofthe focusing positions in FIGS. 4 through 7. Therefore, the allowabledefocus range with respect to the in-focus state focusing position is ±3steps or less. That is, unless the focusing position is in the range of±3 steps from the in-focus state focusing position, the in-focus statecannot be satisfied.

Therefore, according to this embodiment, when the flat subject isphotographed, the final focusing position is determined so that both ofthe in-focus state focusing positions (peak of the evaluation values forthe auto in-focus operation) of the center in-focus detection regions200 a, 200 b, and 200 c and the in-focus state focusing positions of theperipheral in-focus detection regions 202, 204, 206, and 208 can existin a range of the predetermined allowable defocused amount, and thus,the resolution of the peripheral portion can be improved withoutexcessively degrading the resolution of the center portion.

In each of the in-focus detection regions 200 a, 200 b, 200 c, 202, 204,206, and 208, the image to be photographed is the clearest in the statewhere the focus lens 108 is driven to the in-focus state focusingposition. However, if the focus lens 108 is located in the range of theallowable defocused amount with respect to the in-focus focusingposition, the focus of the image can be satisfied.

In the example of FIGS. 6 and 7, the final focusing position is anintermediate location between the in-focus state focusing position (19)obtained from the center in-focus detection regions 200 a, 200 b, and200 c and the in-focus state focusing position (23) obtained from theperipheral in-focus detection regions 202, 204, 206, and 208. Therefore,the in-focus state focusing positions of the center in-focus detectionregions 200 a, 200 b, and 200 c and the in-focus state focusingpositions of the peripheral in-focus detection regions 202, 204, 206,and 208 are within 6 steps of each other. Therefore, the in-focus statecan be satisfied at the center portion and the peripheral portion.

In addition, in the case where the flat subject is photographed, thefinal focusing position is determined as an average value of thein-focus state focusing positions of the in-focus detection regions 200a, 200 b, 200 c, 202, 204, 206, and 208, or an intermediate positionbetween the maximum and the minimum in-focus state focusing positions ofthe in-focus detection regions.

Also, in a case where the in-focus state focusing positions of theperipheral in-focus detection regions 202, 204, 206, and 208 are within3 steps with respect to the in-focus state focusing positions of thecenter in-focus detection regions 200 a, 200 b, 200 c, the in-focusstate focusing position of the center in-focus detection regions can beset as the final focusing position. In addition, in this case, the finalfocusing position can be obtained by applying a weight to the in-focusstate focusing position of the center in-focus detection regions toobtain the weighted average of the focusing positions on the all of thein-focus detection regions.

Furthermore, the changed amount of the focusing position in each of thesteps can be differentiated by designed values (focusing distance, aresolution of an encoder detecting the focusing position, etc.) of thelens unit in the photographing apparatus 100. Therefore, the number ofsteps of the focusing position corresponding to the allowable defocusedamount varies depending on the kind of lens.

In addition, a method of determining whether the subject is the flatsubject or not from the evaluation values for the in-focus operation,which are sequentially calculated, will be described with reference toFIGS. 3 and 4. First, among the three in-focus detection regions 200 a,200 b, and 200 c on the center portion, the region having the closestdistance to the subject is selected, and then, it is determined that themain subject exists on the selected region. In the example of FIGS. 3and 4, since the distance from the in-focus state focusing position(position 19) of the in-focus detection region 200 b is closest to thesubject, the subject at the in-focus detection region 200 b is the mainsubject, and then, the in-focus state focusing position is set asposition 19.

In addition, the in-focus state focusing positions of the fourperipheral in-focus detection regions 202, 204, 206, and 208 arecompared with the in-focus state focusing position (=19) of the selectedin-focus detection region 200 b. The focusing positions of the in-focusdetection regions 206 and 208 on the lower corners are different fromthe in-focus state focusing position (position 19) of the in-focusdetection region 200 b by 4 steps towards the minimum focal length. Inaddition, the focusing positions of the in-focus detection regions 202and 204 on the upper corners are different from the in-focus statefocusing position (19) of the in-focus detection region 200 b by 6-7steps toward infinity.

Whether a difference between the in-focus state focusing position of thein-focus detection region 200 a and the in-focus state focusingpositions of the peripheral in-focus detection regions 202, 204, 206,and 208 is within a range of twice of the allowable defocused amount,that is, 6 steps of the focusing position is used to determine whetherthe subject is a flat subject. That is, when the difference between themaximum and minimum in-focus state focusing positions of the in-focusdetection regions 200 a, 200 b, 200 c, 202, 204, 206, and 208 is withinthe range of twice the allowable defocused amount, it can be determinedthat the subject is the flat subject. Otherwise, a difference betweenthe in-focus state focusing distances can be used to determine whetherthe subject is flat.

In the example of FIGS. 3 and 4, the in-focus state focusing positionsof the in-focus detection regions 200 a, 200 b, 200 c, 202, 204, 206,and 208 are within a range of 10-11 steps of the focusing position,which is greater than the 6 steps, that is, twice of the allowabledefocused amount, and thus, the subject is determined as a non-flatsubject.

If the subject is not determined to be the flat subject, results ofdetecting the in-focus positions on the peripheral in-focus detectionregions become invalid, and the in-focus state focusing position (19) ofthe in-focus detection region 200 b that is closest to the subject amongthe center in-focus detection regions 200 a, 200 b, and 200 c is set asthe final focusing position. In addition, the focus lens 108 is drivento the final focusing position, and the photographing of the image isperformed.

On the other hand, in the example of FIGS. 5 and 6, the differencebetween the in-focus state focusing position of the center in-focusdetection region 200 a and the in-focus state focusing positions of theperipheral in-focus detection regions 202, 204, 206, and 208 is lessthan the 6 steps, which is twice of the allowable defocused amount, andthe subject is determined as the flat subject.

In a case where the subject is determined as the flat subject, thefocusing position 21 that is the intermediate value between the maximumand minimum in-focus positions is determined as the final focusingposition so that the in-focus state focusing positions of the in-focusdetection regions 200 a, 200 b, 200 c, 202, 204, 206, and 208 are allwithin the range of twice the allowable defocused amount, and then, thefocus lens 108 is driven to the final focusing position.

Therefore, since the focusing position is out of the best focusingposition on the center in-focus detection regions 200 a, 200 b, and 200c, the in-focus state of the center portion is slightly degraded,however, the in-focus state of the peripheral portion can be improved.Hence, the in-focus state of the entire screen can satisfy the standardresolution.

In addition, in order to prevent the in-focus state of the centerportion from being degraded, a process for emphasizing an image contouris performed. The process for emphasizing the image contour can be amatrix processing of 5×5, or any other suitable processing.

In addition, when the flat subject is photographed, if the differencebetween the maximum and minimum in-focus state focusing positions of thein-focus detection regions 200 a, 200 b, 200 c, 202, 204, 206, and 208is not within the range of twice of the allowable defocused amount, afocusing position satisfying the in-focus state of the entire screendoes not exist. Then, an aperture of the diaphragm is reduced to improvethe in-focus state of the entire screen. When the diaphragm is reduced,a depth of field is deepened, degradation of the evaluation values forthe auto in-focus operation can be reduced, the allowable defocusedamount is increased, and the aberration such as the field curvature canbe reduced. As described above, the diaphragm value and the allowabledefocused amount are in proportion to each other, for example, thediaphragm value is changed from F2.8 to F5.6, the allowable defocusedamount is also increased twice.

FIG. 8 is a graph showing, in more detail, an adjacent portion of thefocusing position (19) shown in FIG. 6. As described above, the flatsubject can be determined according to whether the in-focus statefocusing positions of the center in-focus detection regions 200 a, 200b, and 200 c and the in-focus state focusing positions of the peripheralin-focus detection regions 202, 204, 206, and 208 are within 6 steps ofthe position, that is, twice of the allowable defocused amount, or not.Accordingly, the flat subject can be determined using the adjacentportion of the in-focus state focusing position of the center in-focusdetection regions 200 a, 200 b, and 200 c to calculate the evaluationvalues for the auto in-focus operation of the peripheral in-focusdetection regions 202, 204, 206, and 208.

In FIG. 8, the evaluation values for the auto in-focus operation of thein-focus detection regions 202, 204, 206, and 208 are calculated withinthe range of 6 steps that is twice of the allowable defocused amountbased on the in-focus state focusing position of the center in-focusdetection region 200 b, and if there is no peak in the evaluation valuesfor the auto in-focus operation of the in-focus detection regions 202,204, 206, and 208 within 6 steps, the subject can be determined as thethree-dimensional subject. Through the above process, the processingamount to determine a flat subject can be minimized.

In addition, if the subject is the three-dimensional subject, theposture of the photographing apparatus can be determined based on theevaluation values for the auto in-focus operation of the in-focusdetection regions 202, 204, 206, and 208. As shown in FIGS. 3 and 4, ina case where the in-focus state focusing positions of the lower twoin-focus detection regions 206 and 208 are nearer than the in-focusstate focusing positions of the center in-focus detection regions 200 a,200 b, and 200 c are, or in a case where the in-focus state focusingpositions of the upper two in-focus detection regions 202 and 204 arefarther than the in-focus state focusing positions of the centerin-focus detection regions 200 a, 200 b, and 200 c are, it can bedetermined that a near subject such as ground is located on the lowerportion of the screen and a far subject such as sky is located on theupper portion of the screen based on the main subject such as a personon the center portion of the screen. Therefore, in this case, it can bedetermined that the photographing is performed in a state that thescreen is disposed in a horizontal direction.

FIG. 9 shows that the subject of FIG. 2 is photographed in a state thatthe screen is disposed in a vertical direction. In addition, FIG. 10 isa graph showing exemplary evaluation values for auto in-focus operationobtained from the in-focus detection regions when the photographing isperformed in the state of FIG. 9. In this case, with respect to the mainsubject (a dog), the near subject such as ground is located on the lowerportion of the screen (which in FIG. 2 was a side portion of thescreen), and a far subject such as a wall is located on the upperportion of the screen (which in FIG. 2 was the other side portion of thescreen). Therefore, as shown in FIG. 10, the in-focus state focusingpositions of the in-focus detection regions 202 and 206 are located onnearer position than the in-focus state focusing positions of the centerin-focus detection regions 200 a, 200 b, and 200 c, and the in-focusstate focusing positions of the in-focus detection regions 204 and 208are located on farther position than the in-focus state focusingpositions of the center in-focus detection regions 200 a, 200 b, and 200c, and then, it can be determined that the photographing is performed ina state that the screen is disposed in the vertical direction.

Therefore, according to the embodiment described above, the posture ofthe photographing apparatus 100 can be detected without forming anadditional sensor for detecting the posture of the photographingapparatus 100. In addition, based on the result of detecting the postureof the photographing apparatus 100, the AE or the white balance can beoptimally controlled. Therefore, for example, when it is determined thatthe photographing is performed in the state where the screen is disposedin the horizontal direction, it can be assumed that the sky or the sunis located on the upper portion of the screen, and thus, the AE controlcan be performed optimally. In addition, posture data is attached to thephotographed image, and thus, the image can be displayed a vertical orhorizontal position according to the posture during the photographing.

In addition, an example of the operations performed by the photographingapparatus 100 will be described with reference to FIG. 11. First, instep S1, a power of the photographing apparatus 100 is turned on todrive the photographing apparatus 100. The exposure of the CCD 110 isperformed, and the CCD 110 reads image data in step S2. Next, the AEevaluation value is calculated based on the signal of the CCD 110 (stepS3).

In addition, an appropriate AE control value is calculated based on theAE evaluation value calculated in process of step S3 (step S4). Here,the diaphragm value and an appropriate shutter speed value arecalculated. Next, the appropriate AE control value is set (step S5).

In step S6, the image is displayed on the LCD 126 (live view display)based on the signal read by the CCD 110. It is determined that theshutter button 132 is half-pushed (SH1 state) or not in step S7. If theshutter button 132 is in the SH1 state, the process proceeds to step S8.On the other hand, if the shutter button 132 is not in the SH1 state,the process returns to step S2.

The focus lens 108 is driven from the near position (minimum focallength) to the far position (infinity) in step S8. Next, the exposure ofthe CCD 110 is performed and the CCD 110 reads the image signal in stepS9. Then, evaluation values for auto in-focus operation of the in-focusdetection regions 200 a, 200 b, 200 c, 202, 204, 206, and 208 aredetermined based on the signal of the CCD 110 (S10).

The in-focus states in the in-focus detection regions 200 a, 200 b, 200c, 202, 204, 206 are detected based on the evaluation values for theauto in-focus operation in step S11. In addition, it is determinedwhether the subject is a flat subject or not based on the in-focus statefocusing positions of the in-focus detection regions 200 a, 200 b, 200c, 202, 204, 206, and 208 in step S12. Thus, the flat subject can bedetermined according to whether the in-focus state focusing positions ofthe in-focus detection regions are within a predetermined range offocusing position steps. In addition, in the process, since it isdetermined whether the in-focus state focusing positions of the in-focusdetection regions are within a range that is twice the allowabledefocused amount determined in step S17, the flat subject can bedetermined within a range that is wider than twice of allowabledefocusing amount in step S12. In step S13, the posture of thephotographing apparatus is determined based on the in-focus statefocusing positions of the in-focus detection regions.

In step S14, it is determined whether the determination of S12 iscompleted or not. Thus, it is determined whether the evaluation valuesfor auto in-focus operation are obtained as required, and whether thedetermination of the flat subject is completed or not. At the same time,it is determined whether the posture of the photographing apparatus 100is completed or not.

In the case where the determination of the flat subject is completed instep S14, the process continues to step S15. Meanwhile, when it isdetermined that the determination is not completed in step S14, theprocess returns to step S8, the focus lens 108 is further driven, andafter that, the evaluation values for the auto in-focus operation of thein-focus detection regions are calculated.

In step S15, if the subject is the flat subject, the process continuesto step S16, and if the subject is not the flat subject, the processjumps ahead to step S19. In step S16, a determination of the in-focusstates in the in-focus detection regions is performed, and in step S17,it is determined whether the in-focus states in the in-focus detectionregions are within the allowable range. Thus, it is determined whetherthe in-focus state focusing positions of the in-focus detection regionsare within the range of twice of the allowable defocused amount.

In a case where the in-focus states of the in-focus detection regionsare in the allowable range in step S17, of the process jumps ahead tostep S19, and the final focusing position is calculated based on thein-focus state focusing positions of the in-focus detection regions. Ifthe in-focus states of the in-focus detection regions are determined tobe not satisfactory in step S17 (for example, the in-focus statefocusing position slightly exceeds the allowable range), a process ofdriving the diaphragm to increase the allowable defocused amount isperformed in step S18. Next, in step S19, the final focusing position iscalculated based on the in-focus state focusing positions in thein-focus detection regions.

In step S20, the focus lens 108 is driven to the final focusingposition. In step S21, the photographing is performed by operating thecombined diaphragm and shutter. In step S22, a process for emphasizingthe image contours of the photographed image data is performed. Then,the photographing process is completed (END).

According to the embodiment of the present invention described above,the determination of whether the subject is a flat subject is performedbased on the evaluation values for the auto in-focus operation obtainedfrom the in-focus detection regions 200 a, 200 b, 200 c, 202, 204, 206,and 208. In addition, if the subject is a flat subject, the finalfocusing position is determined so that the in-focus state focusingpositions of the in-focus detection regions 200 a, 200 b, 200 c, 202,204, 206, and 208 can be within the range of twice an allowabledefocused amount, and thus, the degradation of the resolution on theperipheral portion of the image caused by the aberration of the lens canbe minimized.

In addition, the focusing position is adjusted even though the user doesnot notice in the case of the flat subject, and thus, an inconvenientoperation such as a mode changing is not necessary. In addition, whenthe flat subject such as a sheet of paper on which characters areprinted is photographed, the degradation of resolution on the peripheralportion of the image can be prevented.

As can be appreciated from the above, according to the photographingapparatus and the photographing method of the embodiments of the presentinvention, the degradation of resolution on the peripheral portion ofthe image can be prevented using a simple structure and simple method.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims.

1. A photographing apparatus comprising: an in-focus state detector fordetecting evaluation values for auto in-focus operation representing anin-focus state of a photographing image from a first in-focus statedetection region disposed on a center portion of the photographingimage, and at least one second in-focus state detection region disposedon a peripheral portion of the photographing image; a flat subjectdeterminer that determines whether a subject to be photographed is aflat subject based on the detection result of the evaluation values forauto in-focus operation; a flat subject focusing position calculatorthat calculates a final focusing position based on the evaluation valuesfor auto in-focus operation obtained from the first and second in-focusdetection regions, when the subject is determined as a flat subject bythe flat subject determiner; and a three-dimensional subject focusingposition calculator that calculates a final focusing position based onthe evaluation value for auto in-focus operation obtained from the firstdetection region, when it is determined that the subject is not a flatsubject by the flat subject determiner.
 2. The photographing apparatusof claim 1, wherein the flat subject determiner determines whether thesubject is a flat subject based on a difference between a focusingposition where the evaluation value for auto in-focus operation of thefirst in-focus detection region is a maximum and a focusing positionwhere the evaluation value for auto in-focus operation of the secondin-focus detection region is a maximum.
 3. The photographing apparatusof claim 1, further comprising: a display unit displaying thephotographing image, wherein the first in-focus detection region isdisplayed on the display unit with the photographing image, and thesecond in-focus detection region is not displayed on the display unit.4. The photographing apparatus of claim 1, further comprising: adiaphragm value controller that changes a diaphragm value based on thedetermination result of the flat subject determiner.
 5. Thephotographing apparatus of claim 1, further comprising: a contouremphasizing controller that changes a process of emphasizing a contourof the image based on the determination result of the flat subjectdeterminer.
 6. The photographing apparatus of claim 1, furthercomprising: a posture determiner that determines a posture of thephotographing apparatus based on the evaluation values for auto in-focusoperation of the first and second in-focus detection regions.
 7. Aphotographing method comprising: detecting evaluation values for autoin-focus operation, which represent in-focus states, from a firstin-focus detection region on a center portion of a photographing imageand at least one second in-focus detection region on a peripheralportion of the photographing image; determining whether a subject to bephotographed is a flat subject based on the result of detecting theevaluation values for auto in-focus operation from the first and secondin-focus detection regions; calculating a final focusing position basedon the evaluation values for auto in-focus operation from the first andsecond in-focus detection regions if the subject is determined as a flatsubject; and calculating a final focusing position based on theevaluation value for the auto in-focus operation obtained from the firstin-focus detection region if the subject is determined to not be a flatsubject.
 8. The photographing method of claim 7, wherein in determiningwhether the subject is a flat subject, the flat subject is determinedbased on a difference between a focusing position where the evaluationvalue for auto in-focus operation of the first in-focus detection regionis a maximum and a focusing position where the evaluation value for autoin-focus operation of the second in-focus detection region is a maximum.9. The photographing method of claim 7, further comprising: displayingthe photographing image, wherein the first in-focus detection region isdisplayed with the photographing image, and the second in-focusdetection region is not displayed.
 10. The photographing method of claim7, wherein in determining whether the subject is a flat subject, adiaphragm value is changed based on the result of determining whetherthe subject is a flat subject.
 11. The photographing method of claim 7,wherein in determining whether the subject is a flat subject, a processof emphasizing a contour of the image is changed based on the result ofdetermining whether the subject is a flat subject.
 12. The photographingmethod of claim 7, further comprising: determining a posture of thephotographing apparatus based on the evaluation values for auto in-focusoperation of the first and second in-focus detection regions.
 13. Acomputer readable medium of instructions for controlling a photographingapparatus, comprising: a first set of instructions for controlling thephotographing apparatus to detect evaluation values for auto in-focusoperation, which represent in-focus states, from a first in-focusdetection region on a center portion of a photographing image and atleast one second in-focus detection region on a peripheral portion ofthe photographing image; a second set of instructions for controllingthe photographing apparatus to determine whether a subject to bephotographed is a flat subject based on the result of detecting theevaluation values for auto in-focus operation from the first and secondin-focus detection regions; a third set of instructions for controllingthe photographing apparatus to calculate a final focusing position basedon the evaluation values for auto in-focus operation from the first andsecond in-focus detection regions if the subject is determined as a flatsubject; and a fourth set of instructions for controlling thephotographing apparatus to calculate a final focusing position based onthe evaluation value for the auto in-focus operation obtained from thefirst in-focus detection region if the subject is determined to not be aflat subject.
 14. The computer readable medium of instructions of claim13, wherein the second set of instructions controls the photographingapparatus to determine whether the subject is a flat subject based on adifference between a focusing position where the evaluation value forauto in-focus operation of the first in-focus detection region is amaximum and a focusing position where the evaluation value for autoin-focus operation of the second in-focus detection region is a maximum.15. The computer readable medium of instructions of claim 13, furthercomprising: a fifth set of instructions for controlling thephotographing apparatus to display the photographing image, wherein thefirst in-focus detection region is displayed with the photographingimage, and the second in-focus detection region is not displayed. 16.The computer readable medium of instructions of claim 13, wherein thesecond set of instructions controls the photographing apparatus todetermine whether the subject is a flat subject and change a diaphragmvalue based on the result of determining whether the subject is a flatsubject.
 17. The computer readable medium of instructions of claim 13,wherein the second set of instructions controls the photographingapparatus to determine whether the subject is a flat subject by changinga process of emphasizing a contour of the image based on the result ofdetermining whether the subject is a flat subject.
 18. The computerreadable medium of instructions of claim 13, further comprising: a sixthset of instructions for determining a posture of the photographingapparatus based on the evaluation values for auto in-focus operation ofthe first and second in-focus detection regions.
 19. The photographingapparatus of claim 1, wherein: the in-focus state detector detectsevaluation values for auto in-focus operation representing an in-focusstate of a photographing image from a first in-focus state detectionregion disposed on a center portion of the photographing image, and aplurality of said second in-focus state detection regions disposed on aperipheral portion of the photographing image.
 20. The photographingmethod of claim 7, wherein: the detecting detects evaluation values forauto in-focus operation representing an in-focus state of aphotographing image from a first in-focus state detection regiondisposed on a center portion of the photographing image, and a pluralityof said second in-focus state detection regions disposed on a peripheralportion of the photographing image.